This invention relates to the fields of pathology and radiology, and, in particular, to a device for finding small abnormalities in excised tissue
The current practice of radiology includes performance of mammography, a form of breast x-ray examination which allows detection of very small abnormal lesions, some of which are potentially cancerous. The current practice of pathology includes examination of excised breast tissue in order to demonstrate and assess the mammographic abnormality. The small size of these lesions is correlated with a very early stage of development, which affords a higher chance for cure if cancerous. These small lesions have the characteristic of being non-palpable (cannot be felt with examination by the hand). In addition, these lesions are usually small enough that they cannot be seen by naked eye inspection of the actual tissue.
Detection of a lesion by mammography, its surgical excision, and diagnosis of its cancerous potential by a pathologist form the basis upon which recommendations for patient treatment are made. In order for these diagnostic/ therapeutic procedures to be effective, (a) the lesion must be found by mammography, (b) the surgeon must excise the appropriate portion of breast tissue containing the abnormality and (c) the pathologist must isolate the specific abnormality in question and examine it microscopically to determine its nature. Failure to adequately perform any aspect of this process may result in unsatisfactory examination of the patient with potentially serious consequences in regard to choosing a subsequent treatment plan. Failure to demonstrate the malignant nature of an unexamined lesion could result in undertreatment of the patient resulting in significant morbidity and possibly death.
In order to remove small, non-palpable lesions detected by mammography, a process known as needle localization has been developed. The needle localization procedure entails placement of a thin radiographically opaque metal wire in the patient's breast. This is accomplished by the examining radiologist using x-ray technique to place the localizing wire in close proximity to the target lesion. The proximity of the wire to the lesion can vary considerably depending on the size of the breast being examined, the overall consistency of the breast tissue and the size of the target lesion. The patient then goes to surgery with the localizing wire inserted through the skin into the breast tissue. This serves to delineate the area of tissue which the surgeon then excises in order to remove the target lesion.
The actual volume of tissue surgically removed will vary greatly, influenced again by factors including breast size, tissue consistency, lesional size and technique of the operating surgeon. A "small" needle localization biopsy specimen may be 6-7 centimeters (cm) in length, 3-4 cm in width and 2-3 cm high. However, biopsy specimens ranging up to as large as 10-12 cm in greatest dimension are not uncommon.
Because the size of the target lesion may be as small as 0.1 cm, it becomes readily apparent that finding the abnormal tissue within the relatively large volume of tissue removed can be difficult. The difficulty of this task is better appreciated when one considers that the lesion is generally not detected by visual inspection or touch due to its dimensions. Once excised, the tissue specimen is then reexamined mammographically to determine whether or not the abnormal area has been included in the tissue removed. A "specimen" mammogram (as opposed to a "patient" mammogram) is made and compared to the original patient mammogram. This specimen image will show the lesion as well as the localizing wire. Once removal is confirmed, the patient, usually under general anesthesia, can be awakened and released from care following appropriate observation. The specimen is then sent to the Pathology department for study.
Tissue analysis by the pathologist includes two separate but interrelated phases of examination, gross and microscopic study. Gross examination is that phase which includes physically handling the tissue and, by visual inspection of its character, selecting portions of the tissue which are then processed for further study. For specimens which exceed 1-2 cm in dimension, this generally implies selection of specific tissue samples which are representative of the disease process. These samples are then processed to yield materials, tissue sections on glass slides, which can be examined by microscope and from which a diagnosis is rendered.
Bearing in mind that microscopic examination of the mammographic lesion is a critical step in the patient treatment process, a pathologist currently uses one of several techniques to grossly examine the tissue specimen in an effort to ensure that the target lesion is submitted for microscopic study. The specimen can be submitted in its entirety so as to include all tissue removed. This approach will often yield in excess of 50 tissue samples to be processed and for most institutions would create demands on laboratory resources which make it an impractical alternative.
The generally accepted approach is to examine the tissue using its specimen mammogram as a reference, and, through use of perceived landmarks, including the wire and various distinguishing features in the outer contours of the specimen, select and submit enough tissue so as to reasonably expect inclusion of the lesion. In practical terms, precise submission of the lesional tissue can be difficult due to change in position of the specimen between the time its specimen mammogram is prepared and gross examination is performed, due to lack of definitive reference markings on the mammogram or specimen to use during tissue selection and due to the fact that the wire marker may be located a substantial distance from the lesion. An additional approach is to submit the specimen to the pathologist twice, initially to be divided into a number of smaller pieces which are then re-examined by x-ray. The smaller specimen pieces are then sent back to the pathologist with the second specimen film which ideally localizes the abnormality to a smaller volume of specimen tissue. This technique requires repeat examinations by both the radiology and pathology departments. This approach may reduce but does not completely eliminate the basic problems described above.
These factors collectively make examination of such specimens a difficult task. If the lesion is, despite usual and customary technique, not submitted, or if a second incidental lesion is studied and misinterpreted as representing the target lesion, an erroneous diagnosis may be rendered. The present invention addresses these practical concerns and offers greatly improved potential for precise submission of lesional tissue.